Portable retaining structure

ABSTRACT

A portable marine structure for use as an artificial island and retaining support for fill material includes a tank member having a base member and a wall member sealed to the base member and capable of being flooded with water and sunk in a body of water with flood water to be replaced by select fill material, that may or may not be frozen to resist ice forces against the retaining structure. The floatable structure also includes an outer shell having an outer wall member spaced from and surrounding the tank wall member and a truss system connecting the tank wall member to the outer wall member. The outer shell is open at top and bottom. The artificial island structure is created by floating the marine structure to a desired water location, sinking the structure by flooding the tank with water and then anchoring the structure by filling the outer shell with fill material. When the structure is to be salvaged, it is floated by removing the fill material from the outer shell and removing water from the tank member.

D United States Patent 1 1 1 1 3,740,956

Guy et al. June 26, 1973 PORTABLE RETAINING STRUCTURE [57] ABSTRACTlnvemofsl Al'ullll PY Houston; David A portable marine structure for useas an artificial is- Galloway, slmomon, both of land and retainingsupport for fill material includes a [73] Assign: E880 ProductionResearch Company, tank member having a base member and a wall memberHouston Tex sealed to the base member and capable of being flooded withwater and sunk in a body of water with Filedi 12, 1970 flood water to bereplaced by select fill material, that [21 APPL No: 198,127 may or maynot be frozen to resist ice forces against the retaining structure. Thefloatable structure also includes an outer shell having an outer wallmember [52] US. Cl. 61/465, 62/260 spaced from and surrounding the tankwall member [5 l 1 Int. Cl E02! 21/00 and a truss system connecting thetank wall member to [58] Field of Search 61/46, 46.5, 50, the outer wallmember The outer hell is open at top 36 62/260 and bottom. Theartificial island structure is created by floating the marine structureto a desired water loca- References Cited tion, sinking the structure byflooding the tank with UNITED STATES PATENTS water and then anchoringthe structure by filling the 2,472,869 6/1949 Travers, Jr 61/46 withfill material when the Structure is to 3,429,128 2/1969 Stafford et al.61/46 be salvaged, it is floated y removing the fill material 2,475,8887/1949 Hackett 61/46 from the outer shell and removing water from thetank 2,940,266 6/1960 Smith 61/465 member.

OTHER PUBLICATIONS Oil & Gas Journal of Sept. 14, 1970, pages 60, 61.

12 Claims, 8 Drawing Figures PAIENIEBmzs ms 1 3.740.956

l0 FIG. I.

DrillPipe 7 ARTHUR L.GUY,

i 5: DAVID E. GALLOWAY, T INVENTORS FIG. 8. BY

' JOHN S. SCHNEIDER,

ATTORNEY.

1 PORTABLE RETAINING STRUCTURE BACKGROUND OF THE INVENTION The presentinvention concerns creatinga portable, salvageable, artificial islandstructure for use in shallow water depths, preferably as an oil or gaswell drilling and/or production platform. More particularly, theinvention concerns a thin wall marine structure capable of being floatedto a desired water location, sunk at that location to form an artificialisland and then later raised and salvaged.

Although artificial island fills using conventional sheet pileenclosures have been used for a number of years for near shore oiland/or gas drilling and production facilities, no portable retainingartificial wall island structures have heretofore been constructed orproposed. The marine structure of the present invention reducesfabrication, installation and salvage costs to a minimum. It isparticularly useful in oil orgas exploratory operations because as anoffshore drilling 'platform structure it is readily salvageable andmovable to new locations.

SUMMARY OF THE INVENTION Briefly, the invention comprises a portable,floatable barge structure capable of providing a retaining wall forselect fill material and of, forming an artificial island which includesa tank member capable of being flooded with liquid and sunk in a body ofwater and having a base member and a wall member sealed to the basemember; and an outer shell connected to the tank member comprising anouter wall member spaced from and surrounding the tank wall member and atruss system connecting the tank wall member to the outer wall member toprovide support for the retaining wall during tow member.

The invention also encompasses a method for creating and salvaging anartificial island structure in which the structure is set at desiredlocations in water and removed therefrom.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view showing themarine structure of the invention under tow;

FIG. 2 is a top view of the marine structure shown in FIG. 1;

FIG. 3 is a side view of the marine structure of FIG. 1 showing it sunkon water bottom;

FIG. 4 is another side view of the marine structure of FIG. 1 showing itposition on water bottom with the outer shell and tank member loadedwith removable fill material;

FIG. 5 is still another side viewof the marine structure of FIG. Ipositioned on water bottom illustrating use of the structure in drillingoperations;

FIG. 6 is a ,top view of a portion of the outer shell of the marinestructure of FIG. 1 illustrating freezing of fill material contained inthe outer shell; and

FIGS. 7 and 8 are, respectively, top and side views of the marinestructure of FIG. 1 illustrating a modified towing operation.

DETAILED DESCRIPTION OF THE INVENTION As seen in FIGS. 1 and 2 abuoyant-type marine barge structure, generally designated 10, is formedby a large diameter inner tank having a vertically extending wallsection 14 and a horizontally extending base member 15 sealed to thebottom of wall section 14. Although tank 20 is shown as cylindrical forpurposes of illustration, it may be square or rectangular or of whatevergeometric configuration is required for stability of tow and/or ease inassembly and positioning. An outer, vertically extending wall section 12of a desired geometric configuration which normally would be circular indesign, as shown, is connected by means of a truss system 13 to theinner wall section 14 to form an outer shell designated 11. Tank 20 mayalso be provided with structural support members such as grid workdesignated 1311. A top or deck 15a (see FIG. 5) may be provided to coverat least a portion of the top area surrounded by wall section 14.

The barge structure is made in a conventional manner. It may beconstructed either by welding individual sheets together to form thecircular or ring sections or it may be constructed from rolled sheetswhich are unrolled and assembled at the construction site. The trusssystem 13 may be formed by standard construction beams. Water depth,local bottom conditions, and the available draft to any desired locationdetermines the overall size, geometric configuration, and buoyancyrequirements for the tank 20. The total vertical height for wall members12 and 14 is that needed for total water depth which may include anice-forming area (for aretic waters) plus necessary freeboard height.The relative dimensions of the inner (tank) and outer shells aredependent on the type of fill material used. Development of a fullpassive resistance to the expected overloading or surcharge is desired.The walls 12 and 14 must be spaced sufficiently to achieve independentloading from ice and surcharge (overloading) in order to develop thefull strength of the barge structure installation. The primary purposeof the outer shell 11 is to provide a retaining wall for the fillmaterial placed inside the outer shell. When in sunken position andadequately anchored with fill material, the structure should provideadequate resistance from sliding at the base when subjected to iceloads. The circular shape is preferred in artic waters to increase thestrength level of the barge structure against crushing by ice. Theoverall dimensions of the outer shell should be adequate to provide aretaining wall for the mass required to resist sliding and overturningforces imposed on the barge structure by wave forces or by ice forcesand, if needed, to provide adequate working space for drilling andproduction operations on top of the structure.

Truss system 13 supports the barge structure during towing and settingoperations. It also provides additional support required to resist iceforces on the barge structure.

'As an example of the dimensions for the barge structure that might berequired in arctic waters, the outer wall 12 might have a diameter of300 feet and inner wall 14 might have a diameter of feet. The over-allheight of each wall may be 35 feet where the water level 16, above thewater floor 17, is 14 feet, the layer of ice is 6 feet and the freeboardheight is 15 feet. As previously mentioned, inner tank 20 is sized toprovide buoyancy needed to transport the barge structure 10. However, toprovide stability during towing and setting operations, additionalbuoyancy-tank volume, indicated by dotted lines 21, may be provided inthe space 22 between the two vertical walls 12 and 14.

The base or bottom section 15 of tank 20 is provided with means such assea cocks 25 to permit flooding and sinking of structure once it hasbeen towed to the desired location. A plurality of tubular conductormembers 26 extend from base member to the top of the tank to providedrill stem access to water floor 17 without penetrating base member 15.

Tank 20 is capable of accommodating various proposed uses of thestructure. If it is desired to use tank 20 for dry storage, hydrocarbonstorage, or for otherv purposes, then the truss system within tank 20would be designed to accommodate these loads. When tank 20 is to be usedas a support for drilling loads, then it might be filled with selectfill materials as illustrated in FIG. 4. The entire structure may betowed as a single unit or in separate units that may be assembled on thelocation for the structure. Prior to towing the barge structure to adesired location a drilling rig and/or production equipment may beplaced aboard tank 20. The select material may be sand or coarse grainedmaterial as opposed to silt and fine clay.

In operation, barge structure 10 after fabrication is towed, asillustrated in FIG. 1, to a desired water location. Once located at thedesired site, tank 20 is flooded by means of sea cocks 25, or thesurrounding water might be pumped into tank 20, and the structure sinksto water floor 17 as shown in FIG. 3. The outer shell is then filledwith the select fill material to the extent necessary. It may be leveledwith the top of outer wall 12 as shown. As indicated in FIG. 4, ifdesired, the liquid in tank 20 may also be displaced with fill material.

As shown in FIG. 6 a refrigeration system indicated at 30 may beinstalled in outer shell 11 to freeze the fill material adjacent toouter wall 12. Freezing the fill material may be required if thestructural capacity to resist ice forces is not provided by the fillmaterial outer wall and the truss system. Moisture may be added to thefilm material where necessary to permit the freezing operation to occur.

When it is desired to move barge structure 10 from a particularlocation, the till materials are removed. The fill material may bedispersed by means of water jets and then the water and fill materialmixture pumped out by means of large pumps. The water in tank 20 is thenpumped from the tank to make it again buoyant. The barge structure isfloated in that manner and then towed to any other desired location.If'the fill materials are relatively inaccessible in the area of thebarge structure location, it is possible to recover the material in thesame manner hydraulically dredged material is recovered by pumping thematerial directly into a barge and permitting water to flow off, leavingthe fill materials to be reused.

As seen in FIGS. 7 and 8, removable false work 23 may be added toprovide better tow characteristics for barge structure 10 when the towis to cover long distances and tow characteristics might presentproblems. Although not shown, additional false framework may be addedaft, if desired. Also, a sea anchor 24 may be attached to the aftsection to aid tow stability.

Changes and modifications may be made in the illustrative embodimentsshown and described herein without departing from the scope of theinvention as defined in the appended claims.

Having fully described the nature, objects, method, apparatus andadvantages of our invention, we claim:

1. A marine barge structure capable of providing a thin retaining wallfor fill material comprising:

a floatable tank capable of being flooded and sunk in a body of waterand having a base member and a wall member sealed to said base member;and

an outer shell connected to said tank comprising a thin outer wallmember spaced from and surrounding said tank wall member and truss workmeans connecting said tank wall member to said outer wall member;

the space between said outer wall member and said tank wall member beingopen at the top and bottom. 2. A structure as recited in claim 1including said tank having dimensions sufficient to provide adequatebuoyancy to float said structure.

3. A structure as recited in claim 1 including piping extending throughsaid base member for flooding said tank to cause sinking of saidstructure.

4. A structure as recited in claim 1 including refrigeration meansarranged in said outer shell for freezing fill material when said fillmaterial is located in said outer shell.

5. A structure as recited in claim 4, in which said tank is ofcylindrical shape.

6. A method for creating a portable retaining structure comprising:

a floatable tank capable of being flooded and sunk in a body of waterand having a base member and a wall member, and an outer shell connectedto said tank comprising a substantially vertical outer thin wall memberspaced from and surrounding said tank wall member and connected to saidtank wall member by framework comprising the steps of:

positioning said structure in a body of water;

flooding said tank to sink said structure to water bottom; and

adding fill material to said outer shell to anchor said structure onwater bottom.

7. A method as recited in claim 6, including the step of towing saidstructure to said position in said body of water to provide adequatestructural strength to reduce ice crushing forces in arctic waters.

8. A method as recited in claim 7 including freezing at least a portionof said full material after said structure has been sunk to waterbottom.

9. A method as recited in claim 8 including displacing said liquid inthe tank with fill material after said tank has been flooded and sunk towater bottom.

10. A method for creating a portable retaining structure and artificialisland and removing same using a structure which comprises a floatabletank capable of being flooded and sunk in a body of water having a basemember and a wall member and an outer'shell connected to said tankcomprising a substantially vertical outer thin wall member spaced fromand surrounding said tank wall member and connected to said tank wallmember by truss work, the space between said outer wall member and saidtank wall member being open at the top and bottom comprising the stepsof:

flooding said tank to sink said structure to water bottom;

adding fill material to said outer shell to anchor said structure onwater bottom;

removing said water from said tank to buoy said structure; and

removing said fill material from said outer shell.

11. A marine barge structure capable of providing a thin retaining wallfor fill material comprising:

a buoyant floatable tank capable of being flooded and sunk in a body ofwater and having a base member and a wall member sealed to said basemember;

an outer shell connected to said tank comprising a thin outer wallmember spaced from and surrounding said tank wall member and truss workmeans connecting said tank wall member to said outer wall member;

the space between said outer wall member and said tank wall member beingopen at the top and bottom thereof;

additional buoyancy means located in said outer shell; and

said tank buoyancy and said additional buoyancy means being adequate tofloat said structure.

12. A marine barge structure capable of providing a thin retaining wallfor fill material comprising:

a buoyant floatable tank capable of being flooded and sunk in a body ofwater and having a base member and a wall member sealed to said basemember;

an outer shell connected to said tank comprising a thin outer wallmember spaced from and surrounding said tank wall member and truss workmeans connecting said tank wall member to said outer wall member;

the space between said outer wall member and said tank wall member beingopen at the top and bottom thereof;

fill material located in said outer shell; and

refrigeration means arranged in said outer shell for freezing at least aportion of said fill material.

1. A marine barge structure capable of providing a thin retaining wall for fill material comprising: a floatable tank capable of being flooded and sunk in a body of water and having a base member and a wall member sealed to said base member; and an outer shell connected to said tank comprising a tHin outer wall member spaced from and surrounding said tank wall member and truss work means connecting said tank wall member to said outer wall member; the space between said outer wall member and said tank wall member being open at the top and bottom.
 2. A structure as recited in claim 1 including said tank having dimensions sufficient to provide adequate buoyancy to float said structure.
 3. A structure as recited in claim 1 including piping extending through said base member for flooding said tank to cause sinking of said structure.
 4. A structure as recited in claim 1 including refrigeration means arranged in said outer shell for freezing fill material when said fill material is located in said outer shell.
 5. A structure as recited in claim 4, in which said tank is of cylindrical shape.
 6. A method for creating a portable retaining structure comprising: a floatable tank capable of being flooded and sunk in a body of water and having a base member and a wall member, and an outer shell connected to said tank comprising a substantially vertical outer thin wall member spaced from and surrounding said tank wall member and connected to said tank wall member by framework comprising the steps of: positioning said structure in a body of water; flooding said tank to sink said structure to water bottom; and adding fill material to said outer shell to anchor said structure on water bottom.
 7. A method as recited in claim 6, including the step of towing said structure to said position in said body of water to provide adequate structural strength to reduce ice crushing forces in arctic waters.
 8. A method as recited in claim 7 including freezing at least a portion of said full material after said structure has been sunk to water bottom.
 9. A method as recited in claim 8 including displacing said liquid in the tank with fill material after said tank has been flooded and sunk to water bottom.
 10. A method for creating a portable retaining structure and artificial island and removing same using a structure which comprises a floatable tank capable of being flooded and sunk in a body of water having a base member and a wall member and an outer shell connected to said tank comprising a substantially vertical outer thin wall member spaced from and surrounding said tank wall member and connected to said tank wall member by truss work, the space between said outer wall member and said tank wall member being open at the top and bottom comprising the steps of: flooding said tank to sink said structure to water bottom; adding fill material to said outer shell to anchor said structure on water bottom; removing said water from said tank to buoy said structure; and removing said fill material from said outer shell.
 11. A marine barge structure capable of providing a thin retaining wall for fill material comprising: a buoyant floatable tank capable of being flooded and sunk in a body of water and having a base member and a wall member sealed to said base member; an outer shell connected to said tank comprising a thin outer wall member spaced from and surrounding said tank wall member and truss work means connecting said tank wall member to said outer wall member; the space between said outer wall member and said tank wall member being open at the top and bottom thereof; additional buoyancy means located in said outer shell; and said tank buoyancy and said additional buoyancy means being adequate to float said structure.
 12. A marine barge structure capable of providing a thin retaining wall for fill material comprising: a buoyant floatable tank capable of being flooded and sunk in a body of water and having a base member and a wall member sealed to said base member; an outer shell connected to said tank comprising a thin outer wall member spaced from and surrounding said tank wall member and truss work means connecting said tank wall member to said outer wall member; the space betweeN said outer wall member and said tank wall member being open at the top and bottom thereof; fill material located in said outer shell; and refrigeration means arranged in said outer shell for freezing at least a portion of said fill material. 